1. Field of the Invention
The present invention relates to an endoscope bending portion and a manufacturing method of a bending tube which forms the endoscope bending portion.
2. Description of the Related Art
In general, an endoscope includes an elongated insertion portion configured to be inserted into a body cavity and an operation portion connected to a proximal end side of the insertion portion. The insertion portion includes an elongated flexible tube having flexibility, a bending portion that is connected to a distal end side of the flexible tube and operated to bend, and a distal-end hard portion connected to a distal end side of the bending portion. The bending portion includes a bending tube, and an envelope tube made of, e.g., a rubber material and coating an outer peripheral surface of the bending tube. The bending tube is formed by arranging nodal rings along the longitudinal direction of the endoscope bending portion in line and coupling these nodal rings to allow each of them to rotate. A front-end nodal ring which is the nodal ring closest to the distal-end hard portion is coupled with the distal-end hard portion, and a rear-end nodal ring which is the nodal ring closest to the operation portion is coupled with the flexible tube.
Japanese Examined Utility Mode Application Publication No. Sho 61-21042 (1986) discloses an endoscope bending portion having a configuration that strip-like nodal ring preliminary bodies are formed into circular shapes to provide nodal rings and the nodal rings are coupled with each other to allow each of them to rotate.
JP-A 2007-185314 (KOKAI) discloses a manufacturing method of a bending tube in which a plate-like member is pressed to continuously form strip-like nodal ring preliminary bodies, the nodal ring preliminary bodies are coupled with each other, and then the nodal ring preliminary bodies are collectively formed into circular shapes. In this manufacturing method of the bending tube, the strip-like nodal ring preliminary bodies are first continuously formed in the plate-like member by press work. Each nodal ring preliminary body includes a pair of first tongue piece portions provided on one end side in the longitudinal direction and arranged to be apart from each other at 180° in the circumferential direction of the nodal ring after formed into the circular shape, and second tongue piece portions provided on the other end side in the longitudinal direction and arranged to be apart from each first tongue piece portion at substantially 90° in the circumferential direction of the nodal ring after formed into the circular shape. Through hole is formed in each of the first tongue portions, and a protruding portion is formed on each of the second tongue piece portions by burring processing.
Further, the nodal ring preliminary bodies are coupled by sequentially coupling the through hole in each of the first tongue portions of each of the circular piece preliminary bodies with the protruding portion of a corresponding second tongue portion of an adjacent nodal ring preliminary body. Furthermore, the nodal ring preliminary bodies are formed into the circular shapes, and both ends of each nodal ring preliminary body are bonded to form a nodal ring. In this manner, the bending tube is formed.